Table 3.

Evidence for and against Hsp60 having cell signalling activity

Hsp60 (evidence against)
Human Hsp60 activation of murine monocytes is due to LPS contamination (Gao and Tsan 2003a, b)
Human Hsp60 fails to induce expression of 96 common cytokine genes in murine macrophages (Gao and Tsan 2004)
Murine Hsp60 fails to activate murine splenocytes (Wang et al. 2005a)
Hsp60 (evidence for)
Human recombinant Hsp60 purified so that LPS contamination was below assay sensitivity, activity of protein blocked by boiling (not same for LPS), polymyxin B had no effect. LPS stimulates NF-κB but Hsp60 did not (Kol et al. 2000)
Human Hsp60 truncation mutants identify equatorial domain as having murine bone resorbing activity (this is not the LPS-binding region of Hsp60) (Meghji et al. 2003)
Human Hsp60 equatorial domain peptides promote activation of murine monocytes (Habich et al. 2004)
NOTE T cells are generally unresponsive to LPS but LPS stimulates T cells to adhere to fibronectin via TLR4 signalling (Zanin-Zhorov et al. 2007)
Human Hsp60 promotes T lymphocyte adhesion to fibronectin even in TLR4-ve cells (Zanin-Zhorov et al. 2003)
Human Hsp60 downregulates T cell signalling and cytokine release and blocks induction of Con A-induced hepatitis (Zanin-Zhorov et al. 2005a)
Human Hsp60 downregulates T cell chemotaxis in vitro and in vivo and selected T cell signalling—effects could not possibly be due to LPS or lipoproteins (Zanin-Zhorov et al. 2005b)
Human Hsp60 but not GroEL or M. tuberculosis Hsp60.2 modulate B cell signalling—again, the effects seen could not be due to LPS (Cohen-Sfady et al. 2005)
Human Hsp60 up-regulates T regulatory cell activity in a TLR2-dependent manner (Zanin-Zhorov et al. 2006)
Peptide p277, 24-amino acid fragment of Hsp60 inhibits (like intact Hsp60) T cell chemotaxis (Nussbaum et al. 2006)
Peptide 277 is beneficial in treating early diabetes (Raz et al. 2007; Huurman et al. 2008))
M. tuberculosisHsp60.2 stimulates a non-classical form of macrophage activation distinct from LPS (Peetermans et al. 1994)
M. tuberculosis Hsp60.2 stimulates endothelial cell adhesion protein synthesis distinct from that of LPS (Verdegaal et al. 1996)
M. tuberculosis Hsp60.1 and Hsp60.2 proteins fail to stimulate human monocyte cytokine after proteinase K treatment (Lewthwaite et al. 2001)
M. tuberculosis equatorial domain, but not apical or intermediate domains contain monocyte-activating activity (Tormay et al. 2005)
Inactivation of hsp60.1 gene in M. tuberculosis generates an isogenic mutant that fails to induce a pro-inflammatory response (Hu et al. 2008)
M. tuberculosis Hsp60.2 protein fails to activate or inhibit bone resorption or osteoclast formation [LPS is a potent osteolytic agent] (Winrow et al. 2008)
M. tuberculosis Hsp60.1 protein is a potent inhibitor of osteoclast formation and bone breakdown in vitro and in vivo. Activity cannot be due to LPS contamination as LPS is a potent osteolytic agent (Winrow et al. 2008)
M. tuberculosis Hsp60.1 (but not Hsp60.2 which has equal LPS contamination) inhibits experimental allergic asthma in mice (Riffo-Vasquez et al. 2004)
M. leprae Hsp60.2 but not M. tuberculosis Hsp60.2 or Hsp60 proteins from Streptococcus pneumoniae, Helicobacter pylori or bacillus Calmette-Guérin inhibits experimental asthma in mice (Rha et al. 2002) [note the M. leprae and M. tuberculosis proteins exhibit 95% sequence identity]
A. actinomycetemcomitans Hsp60 stimulates bone breakdown in explants of C3H/HeJ (TLR4-ve) mouse bone (LPS inactive) (Kirby et al. 1995)
Purified H. pylori Hsp60 stimulates macrophage cytokine synthesis via a TLR2/TLR4/Myd88-independent mechanism (LPS acts via a TLR4/Myd88 mechanism) (Gobert et al. 2004).
Recombinant Rhizobium leguminosarum Hsp60.3, but not recombinant Hsp60.1 (70% sequence identity and both with similar (low) LPS levels), stimulates human monocyte pro-inflammatory cytokine synthesis (Lewthwaite et al. 2002)